1. Field
One embodiment of the present invention relates to an information recording device that records data of different purposes and kinds such as compressed motion picture data and audio data to an information recording medium (or information storage medium) such as an optical disk that records such data, an information reproducing method that reproduces data from the medium, and an information recording medium.
2. Description of the Related Art
In recent years, high picture quality and high performance DVDs (digital versatile disks) and DVD video players for reproducing the disks have spread widely, and there are many selections, including peripheral devices that reproduce the multi channel audio thereof, so that environments have been already prepared where home theater systems are available in private homes, and movies, animations and the like can be freely enjoyed there.
Further, in these several years, along the improvement of image compression technologies, and for realization of further higher picture quality, there is an increasing demand for recording high picture quality contents of high definition TV method (hereinafter, referred to simply as HD method) among contents developers. According to this trend, there is a demand for improvements in picture quality also in the expression performance of sub-picture information that has been used as subtitles and menu information.
As a conventional sub-picture information compression technology, there is known a sub-picture image data encoding/decoding system using a run length compression method in which image data of continuous sub-pictures are all replaced into a form of the continuous number of image data and one of the image data thereof, and thereby image data is compressed (for example, refer to Japanese Patent KOKAI Publication No. 8-242448 (paragraphs [0081] to [0101], and FIG. 5)).
For the sub-pictures as subtitles and menu information to high picture quality HD (high definition) contents, contents developers demand the expression performance of 16 colors or higher. However, the sub-pictures handled in the Japanese Patent KOKAI Publication No. 8-242448 are of 2 bits/pixel expression (4 colors) for the conventional SD (standard definition) TV method (hereinafter, referred to simply as SD method). Accordingly, the expression performance thereof is poor for the use as subtitles and menu information in high picture quality HD contents, and a run length compression method of 4 bits/pixel expression (16 colors) is proposed (for example, refer to Japanese Patent KOKAI Publication No. 2004-186808 (paragraphs [0045] to [0047], and FIG. 7)).
However, even with the 4 bits/pixel expression (16 colors) disclosed in the Japanese Patent KOKAI Publication No. 2004-186808, jagged portions appear conspicuous around displayed subtitle characters in some backgrounds (bright portions) of a high definition main picture, which deteriorates high picture quality contents.